MET-SR 71SR

Common issues

• Bearing wear (journal and thrust bearings) leading to excessive axial/radial play and vibration.
• Turbine nozzle ring and blade fouling/erosion, particularly with HFO operation, reducing efficiency and increasing exhaust back pressure.
• Compressor wheel fouling or foreign object damage (FOD) from intake air, causing imbalance and reduced air delivery.
• Oil leakage from bearing housing seals (labyrinth seals or piston rings), leading to oil ingress into exhaust gas or air side.
• Exhaust gas leakage from casing joints, especially between turbine casing and gas inlet/outlet pipes, due to thermal cycling.
• Rotor imbalance due to blade damage, fouling, or bearing issues, resulting in excessive vibration and potential catastrophic failure.
• Turbocharger surging, often due to engine operational issues or severe fouling, which can damage compressor blades and bearings.

Inspection checklist

• Check bearing axial and radial clearances (if inspection covers are removed or during overhaul) against manufacturer's limits.
• Inspect turbine blades and nozzle ring for fouling, erosion, cracks, burning, and foreign object damage. Ensure free movement of VGT (Variable Geometry Turbine) components if fitted.
• Examine compressor wheel for fouling, erosion, cracks, and foreign object damage. Check air filter condition.
• Verify oil supply and drain lines for leaks, proper flow, and cleanliness. Check oil pressure and temperature at inlet/outlet.
• Inspect turbocharger casing for cracks, hot spots, exhaust gas/oil leaks, and tightness of all securing bolts.
• Monitor turbocharger speed, exhaust gas temperatures (inlet/outlet), and scavenge air pressure for deviations from normal operating parameters.
• Check sealing air pressure and flow (if applicable) to prevent oil ingress into the air/gas stream.
• Assess vibration levels using portable or permanently installed monitoring equipment; trend analysis is crucial.
• Inspect insulation on hot surfaces for integrity and absence of oil contamination.

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Complete set of journal and thrust bearings (including bearing bushes, thrust pads, and associated hardware).
• Oil sealing rings / labyrinth seals (for both turbine and compressor sides).
• Gasket and O-ring sets for casing joints, oil lines, and inspection covers.
• Nozzle ring (especially if operating with high sulfur HFO or known issues with erosion/fouling).
• Air filter elements (if applicable to the specific intake arrangement).
• Speed sensor and associated wiring.
• Set of securing bolts and nuts for critical casing sections.

Safety

• High temperature surfaces (turbine casing, exhaust pipes) pose severe burn hazards; ensure insulation is intact.
• High-speed rotating machinery (rotor assembly) presents a risk of entanglement or disintegration if not properly maintained or if overspeed occurs.
• Pressurized systems (exhaust gas, scavenge air, lubricating oil) can cause injury if leaks occur or components fail.
• High noise levels during operation necessitate hearing protection in the vicinity of the turbocharger.
• Potential for oil mist ignition or fire if oil leaks onto hot surfaces, especially in the exhaust gas path.

Class survey

Class surveyors typically check the general external condition for cleanliness, absence of oil/exhaust gas leaks, and integrity of insulation. They will review maintenance records, running hours, and previous survey reports. If the turbocharger is opened for maintenance, they will witness bearing clearance measurements (axial and radial play) and inspect the condition of the turbine and compressor wheels, nozzle ring, and casings. They may also verify the functionality of safety devices like the overspeed trip and alarm systems, and confirm securing arrangements are sound.

Estimated lifetime: 16,000 - 24,000 hours before major overhaul (including bearing replacement and rotor balancing)